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      <h1 class="entry-title">資料傳輸速率計算</h1>
      <p class="meta"><time datetime="2014-09-27T00:37:54" pubdate>六 27 九月 2014</time></p>
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  <div class="entry-content"><p>數據通信中用以描述資料傳輸速率有三個名詞：鮑速率(baud rate)、資料速率(data rate)、以及有效資料速率(effective data rate)。</p>
<h3>(1) 鮑速率</h3>
<p>鮑速率為傳每秒所送信號變化的次數，包括了頻率、相位、振幅以及它們的混合等型態的變化，可以用一個信號時距(Ts)來代表一個位元的傳輸時間，故鮑速率可寫成：
鮑速率 = 1 / Ts
例如某電傳系統中的鮑速率為1200鮑(baud)，則每傳送一個鮑需要0.83mS，若一個鮑僅調變一個位元，則鮑率與以下所講的資料速率相等。</p>
<h3>(2) 資料速率</h3>
<p>資料傳輸調變系統中若採用了混合調變或多位元調變，鮑速率已不足以代表資料傳輸速率，正確的計算應該是：
資料速率 = 鮑率 × 位元數 (bps)
舉例來說，某鮑速率為2400的調幅傳輸系統中，調幅階層變化有256種，表示它可以一次送出8個位元，因此資料速率為2400×8=19200 (bps)，bps就是每秒傳輸的位元數。</p>
<h3>(3) 有效資料速率</h3>
<p>串列傳輸時都會在資料串前後加入一些其他的訊息，有效資料速率是指扣除這些額外訊息後，實際傳輸資料的速率。
有效資料速率 =
資料速率 × 資料位元數 / 資料格式所有位元數
例如一個資料速率為19200 bps的系統以N/8/1非同步格式傳輸，那麼START、STOP各為1位元，資料為8位元，因此
有效資料速率 = 19200 × 8 / (1+8+1) = 15360 (bps)</p>
<p>有效資料速率 = 19200 × 8 / (1+8+1) = 15360 (bps) // 這樣計算方式是因為處理一個8bit 實際上要花10bit 多了 start and stop , 所以 19200(bps) 實際上每秒只能處理 15360(bps)</p>
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<li>參考 http://www.ltivs.ilc.edu.tw/kocp/mpu/m7/m7-3-4.htm</li>
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<time datetime="2014-09-27T00:37:54" pubdate>六 27 九月 2014</time>  <span class="categories">
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